Short-run production

In the traditional and conventional processes, manufacturing parts is expensive and long-time taking. For instance, techniques like injection moulding can even take months and thousands of dollars to produce units and so they make advantage of large volume production to become cost efficient (economies of scale).

However, what if a client demands a small number of units, just for testing? Hence, in this sense, short-run manufacturing plays a crucial role, especially thanks to 3D printing, which has been making it more and more feasible. It simply consists of production of small number of units that allow higher flexibility and shorter lead time than conventional processes. There are different reasons why companies decide to implement this type of production:

• goods are made with the same materials with which they will be produced for to be sold

• to accept the first-to-market philosophy: company tries to introduce a limited quan-tity of products into the market in order to analyse the reaction of consumers and at the same time they produce a bigger quantity batch of the same product

• the product is destined to a market niche, thus it does not require high-volume production

Generally speaking, we can say that companies usually make use of short-run produc-tion for two kinds of products: prototypes, which give the start to mass producproduc-tion and finished goods, meaning products that are ready to be utilized by the final consumer.

2.4.1 Rapid Prototyping

Nowadays the role of prototypes has increased considerably, since it is able to support maximal reuse and innovative combinations of the existing techniques and the quick inte-gration of new ones. However, it has not always been this way: in fact, in the previous decades prototypes were produced only at the end of the planning cycle and they were expensive, required lots of human resources and, as it was not enough, it even took long times since the tools were not always available. Today, instead, prototypes appear in a the early phase of planning and it allows developers, engineers and designers to gain more time and money and save resources.

As mentioned earlier, RP refers to a class of layer-based manufacturing technologies, as Stereolithography, Fused Deposition Modelling, Selective Laser Sintering, Sheet Lam-ination and 3D printing, which operate by gradually adding material layer by layer, and in a total automatic way, differently from the traditional processes.

This technology presents various advantages, among which: any shape or geometric feature can be produced, it allows reduction in time and cost (from 50% to 90%), errors and flaws can be detected at an early stage, it can be used in different industries and fields, discussions with the customer can start at an early stage, assemblies can be made directly in one go, material waste is reduced, no tooling is necessary and last but not least, the designers and the machinery can be in separate places.

However, also some drawbacks characterise RP: the price of machinery and material, the surface is usually rougher than the machined one, some materials are brittle and the strength of RP-parts are weaker in z-direction than in others.

Rapid prototyping represents today the main function of 3D printing; however, the level of technological progress does not allow mass production, even if it is possible to print items in limited quantity with perfect details and complicated forms, as we will be discussing in the next section. Nevertheless, RP is present in almost all sectors, since prototypes are much relevant when it comes to realise a product in large batches or very expensive; among them, there are: aviation, architecture, geography, art and entertainment, automotive, education, jewellery, medical, energy and consumer goods in general.

Figure 2.10: A gear made with the Rapid Prototyping technology [29]

Now we move our attention to a mere economical analysis, in order to figure out which are the main costs involved in manufacturing. Let us start from an equation:

COM_i,t = Pt=t1

t=t0(^Pn_i=1(DM C_t,i+ DLC_t,i) + IDM C_t + IDLC_t) n

where:

• COM_i,t represents the Cost Of Manufacturing in the t investigation time (from t₀ to t₁) at producing unit i

• DMC_i,t represents the Direct Material Cost, so that the cost of any materials used in the final product, in the t investigation time (from t₀ to t₁) at producing unit i

• IDMC_i,t represents the InDirect Material Cost, so that costs for activities or services that benefit more than one project, in the t investigation time (from t₀ to t₁) at producing unit i

• DLC_i,trepresents the Direct Labour Cost, so that labour costs that can be traced to individual units of products, in the t investigation time (from t₀ to t₁) at producing unit i. Sometimes this cost is called touch labour, because workers typically touch the product while making it. For instance, the cost of assembly line workers is a DLC

• IDLC_i,t represents the InDirect Labour Cost, so that labour costs that cannot be physically traced to the creation of products or that can be only traced at a great cost or inconvenience, in the t investigation time (from t₀ to t₁) at producing unit i That equation can be simplified as:

COM_i,t = Pt=t1

t=t0(^Pn_i=1(DM C_t,i+ DLC_t,i) + M OC_t) n

where MOC_i,t represents the Manufacturing Overhead Cost, which includes items as indirect material, indirect labour, maintenance and repairs on production equipment and heat and light, property taxes, depreciation and insurance on manufacturing facilities.

Finally, in order to obtain the Market Price (MP), we should add the Research and Development Costs (RDC), the Revenue (R), Taxes (T) and the Marketing Costs (MC):

M P_i,t = COM_i,t+

Pt=t1

t=t0(^Pn_i=1RDC_t,i+ R_t,i+ T_t,i+ M C_t,i) n

Given those variables, it has been studied that with the Rapid Prototyping, the direct and indirect costs can be importantly lowered with respect to regular linear production chain. Indeed, a recent research conducted on the production of a fork lift model has stated that its estimated cost is 2.5M USD and the production time is 52 weeks. On the other side, comparing this to the digital prototyping the cost would be around 75,000 USD and the production time would instead be 12 weeks.

2.4.2 Rapid Manufacturing

As mentioned earlier, 3D printing is not used for long-run production since it does not represent an advantage concerning time and cost. In fact, in the traditional manufacturing process the most used technology is Injection Moulding, in which parts are produced by injecting molten material into a mould; materials that can be used are various, ranging from metals (die-casting process), glasses, elastomers and confections to thermoplastic and thermosetting polymers. However, the main problem is that the mould is very ex-pensive since it is made by hand or by delicate and sophisticated procedures; reason why, only an high production volume is able to amortize the costs but when it comes to few items production as Additive Manufacturing, and the mould can cost up to 8000 euros, amortization reveals to be hard.

For this reason, AM perfectly commits to Rapid Manufacturing (RM), which employs similar technologies and processes to RP, thus a tool-less manufacturing process. The Figure 3.16 below shows how AM technology for Rapid Manufacturing has been evolving during the last years, passing from 3.9% in 2003 to 42.6% of the total product and service revenues from AM; this market segment, then, grew 66.0% in 2014 to an estimated $.

1,748 billion.

This relevant growth has occurred because of the several advantages that AM has over conventional manufacturing processes; indeed, a producer would change to a new process only if this results to be cost effective, improves product functionality or increases responsiveness. Well, AM seems to meet all these requirements. Here is a list of the main advantages of AM concerning production:

• Reduction of tooling: differently from injection moulding or metal casting, AM reduces or totally eliminates tooling, which leads to benefits as cost and lead times decrease and improvement of product’s time to market

• Agile manufacturing operations: reduction of tooling allows the option of chang-ing a product mix on short notice; in fact, every build on an AM machine can be

Figure 2.11: The use of AM for part production [66]

different, so they can be made on order. In this sense, producers can react more rapidly if market conditions would change and then they can modify production rates to match demand

• Decentralized manufacturing: if we consider a single AM machine capable to build complex part, economies of scale associated with large centralized companies with assembly lines tend to decrease. Reason why, decentralizing manufacturing in a regional or even local basis turns to be economically feasible

• Reduction in inventory and part consolidation: AM is able to reduce inventory by consolidating many parts into one, implying less need for bins for parts on the shop floor, on-site storage and off-site warehousing. Thanks to this, producers have more capital to invest, that can for example be used to develop new products. However, the main benefit consists in the ability to design products with fewer parts but more complex, rather than a large number of simple parts. This, in fact, cuts the overhead related to documentation and production planning and control; moreover, it takes less time and labour to assembly the product, leading to less overall manufacturing costs

• Lightweighting: no tooling and geometric freedom offered by AM allow parts to be to the same functional specifications as traditional parts, but using less material.

• Improved fluid dynamics: the flow efficiency of gases and liquids around or inside a product is strictly dependent on part geometry. Reason why, using the design freedom offered by AM, the optimum geometry can be obtained and at the same time one can get to improved fluid dynamics

However, there are some challenges that AM need to face and that can reduce its economic benefits:

• Cost of machines and materials: most AM machines are expensive to purchase and run, since a small number is sold and vendors need to recoup development costs.

Moreover, machine depreciation lasts several years and it is divided among all the parts it builds. Material represents a direct cost included in the cost of each part and depends on the unit volume. In this sense, materials are expensive because it takes lot of money to produce them; on the other side, thermoplastic filaments used in the extrusion process are even used in the injection moulding one, with the difference that in this latter case the price is relatively low, while in the AM field they seem to be much higher, reason why the cost to the customer is artificially inflated. Only real market competitive conditions could decrease material costs

• Speed and throughput: Of course, a way to reduce the cost of AM parts id to increase the volume of production. How to? Faster operating speeds, larger build envelopes and easier loading and unloading of parts, like with palletized build chambers

• Cost justification: the fact that producing by AM costs too much with respect to the conventional processes is undeniable. However, it is shallow to just make a cost-comparison between the two ways of manufacturing, the traditional one will always have success. What it has to be done is to verify if savings can be found or if the value of a product can be increased. For instance, if a part of an airplane costs $500 dollars using AM while it costs $100 using casting, it does not seem like challenging. Nevertheless, if the weight can be decreased by 25% implying a $5,000 reduction in operating costs for the next 10 years, well, one may think about it

• Traditional attitudes: last but not least, the most difficult challenge to overcome in adopting AM is to convince people stuck on the traditional technology, those who do not feel like taking the risks of a new and unknown technology, and prefer to keep using the old one. Indeed, this problem can be fixed by only promoting the culture of innovation, disseminating the evidence that AM is shaping like the technology of the future. Not easy at all, since it is a challenge both for the manufacturers and for the user community